Intelligence: As more 'red flags' come to light, Mueller disagrees with Bush team's assertions that nothing could have prevented attacks.

WASHINGTON — FBI Director Robert S. Mueller III acknowledged Wednesday that in the weeks before Sept. 11 the bureau missed "red flags" in Minnesota and Arizona that could have led investigators to the terrorist hijackers.

Mueller's sobering concession was at odds with the Bush administration's previous assertions that authorities could not have done anything to disrupt the attacks. And it came even as the FBI disclosed that it had unearthed two additional memos indicating that authorities may have missed terrorist warning signs.

In a 1998 memo, an FBI pilot in Oklahoma City reported to his supervisor that he was suspicious about the "large numbers" of Middle Eastern men receiving flight training at area airports. The pilot said the "recent phenomenon" could be related to "planned terrorist activity." The supervisor who received the memo did not report the suspicions to Washington at the time, and the matter was never investigated, a senior FBI official said.

In a second memo, intelligence officials reported that a Middle Eastern nation had tried to buy a flight simulator in violation of U.S. restrictions. FBI officials on Wednesday did not divulge the date of that memo or the country that tried to buy the simulator. They did say that both documents had been forwarded to members of Congress who are examining why the U.S. intelligence community failed to detect the Sept. 11 attacks in advance and whether warnings were missed.

Although FBI officials downplayed the significance of the two new memos, they appear to fit a pattern of what Mueller described as missed opportunities and lax counter-terrorism analysis. Acknowledging that "we must change," he unveiled an FBI reorganization plan that he said was aimed at developing a more aggressive, proactive approach to pursuing terrorism leads and preventing future attacks.

"There was not a specific warning [before Sept. 11] about an attack on a particular day. But that doesn't mean that there weren't red flags out there, there weren't dots that should have been connected to the extent possible," a contrite and sometimes defensive Mueller told reporters in an extraordinary two-hour briefing. He acknowledged that he himself had unwittingly misspoken last fall in denying the existence of pre-Sept. 11 warnings.

"The jury's still out" on whether the FBI could have done anything to detect what was going to happen on Sept. 11, he said. Had the bureau done a better job of following up on leads around the country, he said, "I can't say for sure that there wasn't a possibility that we would come across some lead that would have led us to the hijackers."

The FBI has come under blistering attack in the last several weeks following disclosures that bureau officials in Washington failed to act last summer either on a warning from an agent in Phoenix about suspicious Middle Eastern flight students or on efforts by agents in Minneapolis to get a search warrant for the computer and personal belongings of flight student Zacarias Moussaoui, who was being held on immigration violations.

In a letter to Mueller last week that has stoked the flames, Coleen Rowley, the general counsel for the FBI in Minneapolis, said officials at headquarters had set up a "roadblock" that prevented her office from pursuing suspicions that Moussaoui was a terrorist. Moussaoui, who authorities now think was planning to be the "20th hijacker," was charged after the attacks with conspiracy and faces the death penalty.

In his briefing Wednesday, Mueller thanked Rowley repeatedly for her critique and said her letter "points squarely to a need for a different approach" toward counter-terrorism.

Mueller, a longtime prosecutor who took over the FBI a week before the attacks, continued to insist that no single episode in Minnesota, Arizona or anywhere else could by itself have led investigators to the Sept. 11 plot. But, he said, "putting all the pieces together over a period of time, who is to say?"

The Phoenix and Minneapolis investigations were both routed through the same FBI office in Washington--the Radical Fundamentalists Unit--but authorities say the unit chief never saw the Phoenix flight-training memo before Sept. 11.

The Phoenix memo, recommending that the FBI canvass flight schools around the country to search for suspicious Middle Eastern students, was remarkably similar to the Oklahoma memo disclosed Wednesday.

That memo, dated May 18, 1998, was titled "Weapons of Mass Destruction." In it, an FBI pilot in Oklahoma City warned that he had "observed large numbers of Middle Eastern males receiving flight training at Oklahoma airports in recent months."